1. Field of the Invention
The present invention generally relates to an ultrasonic receiving apparatus for receiving ultrasonic waves. More specifically, the present invention is directed to an ultrasonic diagnosing apparatus to be used in medical diagnoses by receiving ultrasonic waves from biological bodies with employment of such an ultrasonic receiving apparatus.
2. Description of a Related Art
In conventional ultrasonic diagnosing apparatus, while both ultrasonic transmitting means and ultrasonic receiving means use the same systems, one-dimensional sensor array is generally employed which includes elements (vibrators) for transmitting/receiving ultrasonic waves. The vibrators are realized by using piezoelectric ceramics which is typically known as PZT (Pb(lead) zirconate titanate), or by using a polymer piezoelectric element such as PVDF (polyvinyle difluoride). Furthermore, such a one-dimensional sensor array is mechanically moved so as to acquire two-dimensional images, and those two-dimensional images are synthesized with each other, so that a three-dimensional image is obtained.
However, since there is a time lag along the mechanically moving direction of the one-dimensional sensor array in accordance with this method, tomographic images acquired at different time instants are synthesized with each other, and therefore, the synthesized image becomes blurred. As a result, this conventional method is not suitable for imaging objects to be inspected such as living bodies, for instance, in such a case where ultrasonic echo observations are carried out by employing the above-described conventional ultrasonic diagnosing apparatus.
In order to acquire a three-dimensional image having a high image quality by using ultrasonic waves, a two-dimensional sensor array capable of acquiring a two-dimensional image without being mechanically moved is necessarily required. For this reason, such a method of manufacturing a two-dimensional sensor array with employment of the above-described PZT or PVDF has been considered. In such a case where the above-described PZT or PVDF is employed so as to manufacture such a two-dimensional sensor array, elements must be processed in very fine manners, and also, a very large number of very fine elements must be connected by using wiring lines. However, it is practically difficult to process these elements in a finer manner, and also to manufacture these elements in a higher integration, as compared with the presently-available very fine processing manner and element integration method.
Also, even when these problems could be solved, there are other problems. That is, crosstalk between elements would be increased, electric impedance of elements connected by very fine wiring lines would be increased which deteriorate an S/N ratio thereof, and electrode portions of these very fine elements would be easily destroyed. Under such a circumstance, it is practically difficult to realize such a two-dimensional sensor array with employment of PZT or PVDF elements.
On the other hand, as another ultrasonic sensor without using a piezoelectric material such as PZT, an optical detecting type sensor is known in this field, by which an optical fiber is utilized and an ultrasonic wave is converted into an optical signal to be detected. As such an optical detecting type ultrasonic sensor, the below-mentioned ultrasonic sensors are reported, namely, an optical detecting type sensor using the fiber Bragg grating (will be abbreviated as an xe2x80x9cFBGxe2x80x9d hereinafter) described in xe2x80x9cUnderwater Acoustic Sensor with Fiber Bragg Gratingxe2x80x9d written by TAKAHASHI et al. in National Defense Academy (Japan), see OPTICAL REVIEW Vol. 4, No. 6 in 1997, p. 691-694; and an optical detecting type sensor using the Fabry-Perot resonator (will be abbreviated as an xe2x80x9cFPRxe2x80x9d hereinafter) described in xe2x80x9cFabrication and Performance of a Fiber Optic Micro-Probe for Megahertz Ultrasonic Field Measurementsxe2x80x9d written by UNO et al. in Tokyo Institute of Technology, see T. IEE Japan, Vol. 118-E, No. 11 in 1998, p. 487-492.
If such a two-dimensional sensor array is manufactured by employing these ultrasonic sensors, there are such merits that electric-wiring works to a large number of very fine elements are no longer required, and furthermore, higher sensitivities can be obtained. However, this two-dimensional sensor owns another problem that since this ultrasonic sensor itself is made in high cost, manufacturing cost of a two-dimensional sensor is increased, and also, manufacturing cost of an ultrasonic receiving apparatus using the two-dimensional sensor array is increased.
The present invention has been made to solve the above-described problems. A first object of the present invention is to provide an ultrasonic receiving apparatus capable of detecting an ultrasonic wave in a two-dimensional manner without necessities of electric-wiring works to a large number of very fine elements and without increase of crosstalk and impedance, and furthermore, to manufacture the ultrasonic receiving apparatus in low cost. Also, a second object of the present invention is to provide an ultrasonic diagnosing apparatus capable of acquiring either a two-dimensional ultrasonic image or a three-dimensional ultrasonic image by using the above-described ultrasonic receiving apparatus.
To solve the above-explained problems, an ultrasonic receiving apparatus according to one aspect of the present invention comprises: an ultrasonic detecting element having a reception plane capable of receiving ultrasonic waves, for modulating light on the basis of ultrasonic waves applied to respective positions of the reception plane; and a photodetector having a plurality of pixels, for detecting light output from corresponding positions of the ultrasonic detecting element.
Also, an ultrasonic diagnosing apparatus according to one aspect of the present invention comprises: a drive signal generating circuit for generating the drive signals; transmission means for transmitting ultrasonic waves in response to drive signals; reception means including an ultrasonic detecting element and a photodetector, the ultrasonic detecting element having a reception plane capable of receiving ultrasonic waves and modulating light on the basis of ultrasonic waves applied to respective positions of the reception plane, the photodetector having a plurality of pixels and detecting light output from corresponding positions of the ultrasonic detecting element to thereby output detection signals; signal processing means for receiving the detection signals output from the reception means to process the received detection signals; control means for controlling both generation timing of the drive signals and acquisition timing of the detection signals; image processing means for constructing image data on the basis of an output signal of the signal processing means; and an image display unit for displaying thereon an image on the basis of the image data.
According to the present invention, since the ultrasonic detecting element having the ultrasonic reception plane including positions which correspond to a plurality of pixels of the photodetector is employed, such an ultrasonic receiving apparatus can be manufactured in low cost. That is to say, this ultrasonic receiving apparatus is capable of detecting the ultrasonic waves in a two-dimensional manner without necessities of electric-wiring works to the large number of very fine elements and without increase of crosstalk and impedance. Accordingly, an ultrasonic diagnosing apparatus capable of acquiring a two-dimensional or three-dimensional ultrasonic image with better qualities can be realized by employing such an ultrasonic receiving apparatus.